Interaction of Methane with Single-Walled Carbon Nanotubes： Role of Defects,Curvature and Nanotubes Type

We investigate the interaction of single-walled carbon nanotubes （SWCNTs） and methane molecule from the first principles. Adsorption energies are calculated, and methane affinities for the typical semiconducting and metallic nanotubes are compared. We also discuss role of the structural defects and nanotube curvature on the adsorption capability of the SWCNTs. We could observe larger adsorption energies for the metallic CNTs in comparison with the semiconducting CNTs. The obtained results for the zig zag nanotubes with various diameters reveal that the adsorption energy is higher for nanotubes with larger diameters. For defected tubes the adsorption energies are calculated for various configurations such as methane molecule approaching to the defect sites pentagon, hexagon, and heptagon in the tube surface. The results show that the introduce defects have an important contribution to the adsorption mechanism of the methane on SWNTs.     

Electronics and Structural Properties of Single-Walled Carbon Nanotubes Interacting with a Glucose Molecule: ab initio Calculations

The adsorption of glucose molecule on single-walled carbon nanotubes(SWCNTs)is investigated by density functional theory calculations.Adsorption energies and equilibrium distances are evaluated,and glucose binding to the typical semiconducting and metallic nanotubes with various diameters and chirality are compared.We also investigated the role of the structural defects on the adsorption capability of the SWCNTs.We could observe larger adsorption energies for the larger diameters semiconducting CNTs,while the story is paradoxical for the metallic CNTs.The obtained results reveal that the adsorption energy is significantly higher for nanotubes with higher chiral angles.Finally,the adsorption energies are calculated for defected nanotubes for various configurations such as glucose molecule approaching to the pentagon,hexagon,and heptagon sites in the tube surface.We find that the respected defects have a minor contribution to the adsorption mechanism of the glucose on SWNTs.The calculation of electron transfers and the density of states supports that the electronic properties of SWCNTs do not change significantly after the gluycose molecular adsorption.Consequently,one can predict that presence of glucose would neither modify the electronic structure of the SWCNTs nor direct to a change in the conductivity of the intrinsic nanotubes.     

修饰银电极上单壁碳纳米管的表面增强拉曼散射

本文采用修饰了银纳米颗粒的银电极作为基底,获得了高质量的单壁碳纳米管(SWCNTs)的表面增强拉曼散射(SERS)光谱。在1100~1500 cm-1范围内观测到了一组表征SWCNTs结构的新峰。修饰在银电极上的银纳米颗粒不仅可以保证SWCNTs在这一体系中吸附的紧密性,而且通过变面等离子体共振起到了电磁放大的作用。通过对银纳米颗粒修饰银电极表面SWCNTs的SERS光谱及其随电位变化的SERS光谱的研究,我们可以研究这一过程中的SERS机制。理论和实验结果表明,银纳米颗粒修饰银电极上单壁碳纳米管的SERS很有潜力成为一种检测单壁碳纳米管合成质量的新方法。     

碳纳米管/寡聚胸腺嘧啶复合体系与汞离子作用的光谱研究

利用寡聚胸腺嘧啶核苷酸(PolyT)与碳纳米管(CNTs)之间的自发非共价修饰作用形成稳定的CNTs/PolyT纳米复合体系,采用共振光散射(RLS)和紫外-可见吸收光谱考察了该复合体系与汞离子的相互作用.实验结果表明,水相中单链PolyT能与CNTs形成稳定而均匀的分散体系,而单链Po1yT极易捕获汞离子生成特异性的...     

浓硝酸处理碳纳米管对4-硝基苯酚的吸附性能研究

本文采用浓硝酸氧化法来改性多壁碳纳米管,用Raman光谱、SEM和分光光度计对改性前后的多壁碳纳米管对4-硝基苯酚溶液的吸附能力进行了比较研究。Raman光谱和SEM分析表明浓硝酸处理使碳纳米管端口打开,管变短,并且在表面引入了羟基、羧基等酸性官能团。采用分光光度计测定溶液浓度,计算出浓硝酸处理前后多壁碳纳米管对不同浓度4-硝基苯酚的吸附效率,实验结果表明经浓硝酸处理后的多壁碳纳米管的吸附效率有较大的提高。     

NH自由基与臭氧反应机理的理论研究

用量子化学从头计算方法,在HF／6－31＋＋G**水平研究了臭氧与NH三线态活性自由基反应的微观机理,优化得到反应物、过渡态、中间体和产物的几何构型。用MP2／6－31＋＋G**／／HF6－31＋＋G**方法计算能量,同时进行零点能校正。研究结果表明： NH三线态活性自由基与O3反应首先成稳定中间体NHO3,然后中裂解生成HNO和O2。     

Effects of Radius and Orientation of Single-Walled Carbon Nanotubes on Their Nonlinear Tensile Deformation Behaviour

By capturing the atomic information and reflecting the behaviour governed by a nonlinear potential function, an analytical molecular mechanics approach is applied to establish the constitutive relation for single-walled carbon nanotubes （SWCNTs）. The nonlinear tensile deformation curves of zigzag and armchair nanotubes with different radii are predicted, and the elastic properties of these SWCNTs are obtained. A conclusion is made that the nanotube radius has little effect on the mechanical behaviour of SWCNTs subject to simple tension, while the nanotube orientation has larger influence.     

Theoretical study of ZnO adsorption and bonding on Al_2O_3(0001) surface

Sapphire (α-Al2O3) and silicon (Si) are widely applied as the substrates of the highquality ZnO thin films prepared by pulse laser deposition (PLD) and molecule beamepitaxy (MBE) technology. The adhesion, diffusivity, and bonding of the particles on thesubstrates play a significant role in the forming and initial growing of nucleation for filmgrowth, and directly influence the quality of the entire thin films[1]. No sufficient studiesand experiments are available on the surface atomic str…     

Spectroscopic Studies on Pure and Histidine-Functionalized Multiwalled Carbon Nanotubes

Electron paramagnetic resonance, Fourier transform infrared, and ultraviolet-visible studies were carried out for pure and histidine-functionalized multiwalled carbon nanotubes. Electron paramagnetic resonance absorption spectral data were found to be the best fit for the Gaussian lineshape. The g-values indicate the presence of magnetic impurities in the samples and the interaction between the localized electrons and delocalized electrons in the nanotubes trapped at defects or magnetic ion sites. The electron spin concentration decreases with increasing concentration of histidine, which implies that the unpaired electrons undergo a reduction process in the histidine-functionalized multiwalled carbon nanotubes. Fourier transform infrared study confirms the presence of functional groups in pure and histidine-functionalized multiwalled carbon nanotubes. Ultraviolet-visible study reveals the formation of a charge transfer complex in histidine-functionalized multiwalled carbon nanotubes.     

Theoretical investigations on structural, elastic and electronic properties of thallium halides

Theoretical investigations on structural, elastic and electronic properties, viz. ground state lattice parameter, elastic moduli and density of states, of thallium halides (viz. TlCl and TlBr) have been made using the full potential linearized augmented plane wave method within the generalized gradient approximation (GGA). The ground state lattice parameter and bulk modulus and its pressure derivative have been obtained using optimization method. Young's modulus, shear modulus, Poisson ratio, sound velocities for longitudinal and shear waves, Debye average velocity, Debye temperature and Grüneisen parameter have also been calculated for these compounds. Calculated structural, elastic and other parameters are in good agreement with the available data.     

Study on the doping stability and electronic structure of wurtzite Zn1−xCdxO alloys by first-principle calculations

An ab initio calculation based on density functional theory is applied to study the doping stability and electronic structure of wurtzite Zn_1−xCd_xO alloys. It is found that the different alloy configurations of Zn_1−xCd_xO with a given Cd content are possible thermodynamically, but having different band gaps. With increasing Cd content, the formation enthalpy of Zn_1−xCd_xO alloy increases sharply. The Cd-content dependence of the band-gap values can be fitted with a second-order polynomial. The reduction of band gap can be attributed to the contributions of the hybridization of Zn-4s and Cd-5s, the enhancement of p-d repulsion, and the tensile strain due to Cd-doping.     

Theoretical and experimental investigation on structural and electronic properties of Al/O/Al,O-doped WS2

Effects of the doping atom (O, Al, and (Al, O)) on structural and electronic properties of the monolayer WS₂ have been studied by using first-principles calculations. Results show that the covalent character of W–S bonding has been enhanced after doping. Meanwhile, W–O, Al–S and W–S bonds of (Al, O) co-doped WS₂ monolayer have higher covalent character compared with O-doped and Al-doped WS₂ monolayer of this work. After doping with Al (or Al, O) atoms, Fermi level moves close to the valence band and the dopant atoms produce the defect energy levels, indicating that Al doped and (Al, O) co-doped WS₂ monolayer both have p-type conductivity. O-doped and (Al, O) co-doped WS₂ ultrathin films was prepared on Si substrates. Results of Raman spectra show the formation of the O-doped and (Al, O) co-doped WS₂ films. Moreover, compared with the pure WS₂, the approximate reduction of 0.43 eV and 0.46 eV for W 4f and S 2p in binding energy after (Al, O) co-doped shows that p-type doping of (Al, O) co-doped WS₂ has been verified.     

苯并氧化呋咱稳定性和异构化的DFT和ab initio研究

运用B3LYP/6-31G(d)密度泛函理论（DFT）方法对苯并氧化呋咱、邻二亚硝基苯及其间的异构化反应进行了计算研究。结果表明,苯并氧化呋咱的分子总能量比邻二亚硝基苯的低;由苯并氧化呋咱异构为邻二亚硝基苯的正向反应活化能（Ea+=51.0kJ/mol）,与文献实测值（58.6kJ/mol）较接近,而其逆向反应活化能（Ea-=4.6kJ/mol）很小,从而揭示了苯并氧化呋咱比邻二亚硝基苯更稳定·此外,进行了HF/3-21G、HF/6-31G(d)和MP2/6-31G(d)//6-31G(d)水平下相应的计算,发现B3LYP-DFT的结果较abinitio为优。谐振动频率的B3LYP/6-31G(d)计算还支持了邻二亚硝基苯为苯并氧化呋咱“自-自”互变重排反应的中间体。     

碳纳米管与氨基酸作用的光散射性质研究

研究了在乙醇中超声分散后的碳纳米管(CNT)与氨基酸相互作用的光散射性质.实验考察了激发波长,pH值,CNT浓度和水的百分含量对CNT光散射强度的影响;在优化的实验条件下,发现CNT与白氨酸作用时,CNT的散射强度会随着白氨酸的浓度的增加而增加,但是与天冬酰胺作用时,CNT的散射强度会随着天冬酰胺的浓度的增加而减弱,此方法有望用于对此二种氨基酸的实际分析测定.     

M+AsF6-(M=Li,Na,K,Rb和Cs)离子对的结构和振动光谱

利用abinitio计算方法研究了AsF6-阴离子和M AsF6-(M =Li ,Na ,K ,Rb 和Cs )直接接触离子对的结构和光谱行为。结果表明,具有C3V结构三齿相互作用的M AsF6-最稳定,二齿配位的结构只有在特定条件下才可能稳定存在。当形成离子对后,阳离子与AsF6-的相互作用将改变AsF6-的结构,这其中Li 的影响最大。另外,AsF6-光谱的变化可用来指认溶液中离子的缔合和离子对的种类。     

现场拉曼光谱研究多种铂氧化物还原过程及其对甲醇氧化的影响

采用原位拉曼光谱技术研究方波电位循环氧化还原 (ORC)过程中产生的铂氧化物的还原过程 ,其中过氧化物和超氧化物消失的电位在 0 2V左右 ,晶格氧化物和氧化铂则分别消失在 0V和 -0 2 5V左右。我们还初步探讨了不同还原电位下形成的铂电极表面纳米微粒对甲醇电催化活性的影响     

Theoretical study on adsorption of Au and hydrated Au cations on clean Si(1 1 1) surface

To model the adsorption of Au⁺ cation in aqueous solution on the semiconductor surface, the interactions of Au⁺ and hydrated Au⁺ cations with clean Si(1 1 1) surface were investigated by using hybrid density functional theory (B3LYP) and Møller-Plesset second-order perturbation (MP2) methods. Si(1 1 1) surface was described with Si₇H₁₁, Si₁₁H₁₇ and Si₂₂H₂₁ clusters. The effect of the basis set superposition error (BSSE) was taken into account by applying the counterpoise correction. The calculated results indicated that the binding energies between hydrated Au⁺ cations and clean Si(1 1 1) surface are large, suggesting a strong interaction between hydrated Au⁺ cations and the semiconductor surface. The bonding nature of the chemical adsorption of Au⁺ to Si surface can be classified as partial covalent as well as ionic bonding. As the number of water molecules increases, the water molecules form hydrogen bond network with one another and only one water molecule binds directly to the Au⁺ cation. The Au⁺ cation in aqueous solution will safely attach to the clean Si(1 1 1) surface.     

光谱法研究橙皮素与DNA分子间的相互作用机制

以盐酸小檗碱(BR)为荧光探针,研究了鲱鱼精DNA与橙皮素的相互作用.采用荧光光谱,紫外可见吸收光谱,盐效应,Scatchard方程等手段,探讨了橙皮素与DNA的作用机制.结果表明,在生理酸度(pH=7.4)下,橙皮素对DNA-BR体系的荧光有猝灭作用,猝灭类型为静态猝灭与动态猝灭共存的模式,其作用方式为嵌插和静电作用...     

浓硝酸处理前后多壁碳纳米管的荧光特性研究

对浓硝酸处理前后多壁碳纳米管的荧光特性进行了研究,结果发现多壁碳纳米管在浓硝酸处理前后都能产生荧光;与浓硝酸处理前相比,浓硝酸处理后的多壁碳纳米管的荧光有所增强,且荧光谱峰向短波长方向发生蓝移。碳纳米管产生的荧光与碳纳米管在其缺陷处捕获激发光的能量以及最低空轨道和最高占有轨道之间的能隙有关。多壁碳纳米管在浓硝酸处理前后都有缺陷,因而都能在其缺陷处捕获激发光能量而产生荧光;浓硝酸处理引起多壁碳纳米管的缺陷增多、捕获激发光能量增加因而荧光也随之增强。碳纳米管的最低空轨道和最高占有轨道之间的能隙随其长度减小而增大,浓硝酸处理引起多壁碳纳米管被削短导致其最低空轨道和最高占有轨道之间的能隙增大,因而引起多壁碳纳米管的荧光谱峰向短波方向蓝移。     

荧光光谱法研究拜复乐与小牛胸腺DNA的作用机理

用荧光光谱法研究了拜复乐(MXFX)与小牛胸腺DNA(ctDNA)之间的相互作用。在pH=7.4的TrisHCl缓冲溶液中,MXFX的荧光激发峰和发射峰分别位于291 nm和462 nm。ctDNA的加入对MXFX的荧光有静态猝灭作用,这种荧光静态猝灭作用是由ctDNA和MXFX结合引起的,作用力为氢键或范德华力,结合常数为1.28×105L/mol(25℃)。采用离子强度的影响、碘离子猝灭及溴乙锭竞争作用实验研究了MXFX与ctDNA间的相互作用,结果表明MXFX与DNA的结合是MXFX嵌入到DNA中相邻2个碱基对之间,属于嵌入结合模式。